Intra-operative heart size measuring tool

ABSTRACT

A heart size measuring tool includes a tubular body, a flexible measuring cord having length indicia, a measuring cord support mechanism movable between retracted and extended states with respect to the body, and an actuating mechanism to move the measuring cord support mechanism. When in the retracted state the measuring cord support mechanism is positioned within the tubular body with the measuring cord in a collapsed position. When the measuring cord support mechanism is in the extended state the measuring cord extends around a portion of a heart to be measured. A scale on the body can be used in connection with the indicia on the measurement cord to provide a reading of the heart size.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/261,173, filed on Jun. 29, 2012, which is a United States nationalstage entry of International Application no. PCT/US2010/028830 filedMar. 26, 2010 and entitled “Intra-Operative Heart Sizing Tool,” whichclaims priority to U.S. provisional patent application No. 61/164,183filed Mar. 27, 2009. The contents of these prior applications areincorporated herein by reference in their entirety as if set forthverbatim.

FIELD OF THE INVENTION

The invention is a tool for measuring the size of a heart in situ.

BACKGROUND OF THE INVENTION

Cardiac support devices (CSDs) used to treat heart disease are generallyknown and disclosed, for example, in International Publication No. WO2008/003034 which is incorporated herein by reference in its entirety.CSDs and tools and methods for surgically delivering or implanting thedevices are also generally known and disclosed, for example, inInternational Publication No. WO 2008/011411 which is incorporatedherein by reference in its entirety.

Sizes of diseased hearts can vary. Accordingly, CSDs come in a range ofsizes. Prior to the delivery procedure, a surgeon will typically measurethe size of the patient's heart, and select an appropriately sized CSD.One known approach for measuring the patient's heart size is through CTimaging under fluoroscopy. Heart size measuring tools are also disclosedin the Vanden Hoek et al. U.S. Pat. No. 6,575,921 and the Krueger U.S.Pat. No. 6,179,791.

There is, however, a continuing need for improved measuring tools andassociated methods. In particular, there is a need for heart sizemeasuring tools and methods that are accurate and efficient to perform.

SUMMARY OF THE INVENTION

The invention is an improved intra-operative heart size measuring tool.The tool can be efficiently used to provide accurate measurements of aheart size. One embodiment of the tool includes a tubular body, aflexible measuring cord having length indicia, a measuring cord supportmechanism and an actuating mechanism. The actuating mechanism moves themeasuring cord support mechanism between retracted and extended stateswith respect to the body to drive the measuring cord between a collapsedposition and a measuring position. When the measuring cord is in themeasuring position the measuring cord extends around a portion of theheart to be measured. Another embodiment of the invention includes ascale that can be used in connection with the indicia on the measuringcord to provide a reading of the heart size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of a heart size measuring tool inaccordance with one embodiment of the invention, with the measuring cordsupport mechanism shown in the extended position.

FIG. 2 is an isometric illustration of the heart size measuring toolshown in FIG. 1, with the measuring cord support mechanism shown in theretracted position.

FIG. 3 is an isometric illustration of the distal end of the measuringtool shown in FIG. 1, with the measuring cord support mechanism in theextended state and the measuring cord in a measuring position around theatrioventricular groove of a heart.

FIG. 4 is an isometric illustration of a heart size measuring tool inaccordance with another embodiment of the invention, having a suctioncup and shown with the measuring cord support mechanism in the extendedposition.

FIG. 5 is an isometric illustration of the heart size measuring toolshown in FIG. 4, with the measuring cord support mechanism shown in theretracted position.

FIG. 6 is an isometric illustration of a heart size measuring tool inaccordance with another embodiment of the invention, having ties betweenthe support members of the measuring cord support mechanism and shownwith the support mechanism in the extended position.

FIG. 7 is a detailed illustration of a pair of support members and a tieof the measuring tool shown in FIG. 6.

FIG. 8 is an isometric illustration of a heart size measuring tool inaccordance with another embodiment of the invention, having radiopaquemarkers on the support members of the measuring cord support mechanismand shown with the support mechanism in the extended position.

FIG. 9 is an isometric illustration of a heart size measuring tool inaccordance with another embodiment of the invention, having deflectionsensors on the support members and shown with the support mechanism inthe extended position.

FIG. 10 is an isometric illustration of a heart size measuring tool inaccordance with another embodiment of the invention, having EEG or othersensor electrodes on the support members and shown with the supportmechanism in the extended position.

FIG. 11 is an is isometric illustration of a heart size measuring toolin accordance with another embodiment of the invention, shown with thesupport mechanism in the retracted position.

FIG. 12 is an isometric illustration of the heart size measurement toolshown in FIG. 11, with the support mechanism in the extended andunactuated position.

FIG. 13 is an isometric illustration of the heart size measurement toolshown in FIG. 11, with the support mechanism in the extended andpartially actuated position.

FIG. 14 is an isometric illustration of the distal end of the measuringtool shown in FIGS. 11-13, with the measuring cord support mechanism inthe extended state and partially actuated to extend the measuring cordaround a portion of the atrioventricular groove of a heart.

FIG. 15 is an isometric illustration of the distal end of the measuringtool shown in FIGS. 11-13, with the measuring cord support mechanism inthe extended state and fully actuated to extend the measuring cordaround the atrioventricular groove of a heart.

DETAILED DESCRIPTION

One embodiment of an intra-operative heart size measuring tool 10 inaccordance with the present invention is shown in FIGS. 1-3. Measuringtool 10 includes body 12, measuring cord 14, measuring cord supportmechanism 16, actuating mechanism 18, measuring cord retractionmechanism 17 and scale 19. Body 12 is a generally tubular member havinga distal end 20, proximal end 22 and a plurality of elongated slots 24(six are shown in the illustrated embodiment) extending through the bodyat a location adjacent to the actuating mechanism 18. Actuatingmechanism 18 includes a handle 26 that is slidably mounted to the body12. Engagement structures such as pins 28 on the handle 26 extend intothe slots 24. Measuring cord support mechanism 16 includes a plurality(six are shown) of support members 30 within the body 12. Proximal ends(not visible) of each of the support members 30 are connected to thepins 28 within the body 12. Other embodiments (not shown) include otherstructures operatively coupling the handle 26 to the support members 30.

Support members 30 are elongated and resilient members. Each of thesupport members 30 includes one or more guides 40, shown as loops in theillustrated embodiment, for supporting the measuring cord 14. In theillustrated embodiment, each of the support members 30 has a guide 40located near the distal end of the support member. One of the supportmembers 30 also has a number of guides 40 at spaced locations along itslength. As perhaps best shown in FIG. 3, measuring cord 14 extendsthrough the guides 40 at the ends of the support members 30, and intothe body 12 through the guides 40 along the length of the one supportmember. One end 42 of the measuring cord 14 is fixedly mounted to thebody 12. The other end 44 of the measuring cord 14 is mounted to theretraction mechanism 17. Cord retraction mechanism 17 can be aspring-loaded spool that is biased to wind up slack portions of themeasuring cord 14. Measuring cord 14 has indicia such as graduatedlength markings 46 in the embodiment shown in FIG. 1.

Handle 26 is actuated to drive the measuring cord support mechanism 16between a first or retracted state shown in FIG. 2 and a second orextended state shown in FIGS. 1 and 3. In the retracted state shown inFIG. 2, the support members 30 are in a reduced-diameter configuration.In the illustrated embodiment this configuration is achieved by theactuating mechanism 18 withdrawing the support members 30 completelyinto the distal end 20 of the body 12. In other embodiments (not shown)the support members 30 extend partially out of the body 12 when thesupport mechanism 16 is in its retracted state. When the measuring cordsupport mechanism 16 is in the retracted state the support members 30pull the measuring cord 14 into a collapsed position. Retractionmechanism 17 can retract and retain portions of the measuring cord whenthe support mechanism 16 is in the retracted state. When the measuringcord support mechanism 16 is in the extended state shown in FIGS. 1 and3, the support members 30 extend from the distal end 20 of the body 12.The measuring cord 14 is thereby forced out of the body 12, withportions of the measuring cord being withdrawn from retraction mechanism17 and sliding through the guides 40.

Tool 10 is used to measure the size of a patient's heart. In oneembodiment the measurements taken by the tool 10 can be used to selectthe size of a cardiac support device (CSD) being applied to thepatient's heart. Use of the tool 10 will typically begin with themeasuring cord support mechanism 16 in the retracted state. The distalend 20 of the tool 10 can then be inserted through an opening in thepatient's chest and pericardium (not shown) and positioned at ameasurement position at the apex of the patient's heart. For example,the tool 10 can be inserted through a minimal access site such as athoracotomy. Fluoroscopic guidance can be used to position the tool 10.The tool 10 can be sized or otherwise configured so that the handle 26and scale 19 are located outside of the patient's body when the distalend 20 of the tool is located at the measurement position. The handle 26is then actuated to drive the measuring cord support mechanism 16 to theextended state with the support members 30 extending around the heartand positioning the measurement cord 14 in the measurement positionaround the heart at the target location to be measured. In this andother embodiments the support members 30 can be telescoping. Whenmeasuring the heart for CSD sizing, for example, the circumference ofthe heart at the atrioventricular (A-V) groove will typically bemeasured. However, the circumference of the heart at locations inaddition or as an alternative to the A-V groove can be measured. Oncethe measuring cord 14 is positioned in this manner, the circumference ofthe heart can be read from scale 19 based on the indicia 46 on themeasuring cord. For example, the indicia 46 can be calibrated in such amanner that the indicia closest to a marker on scale 19 represents thecircumference of the heart at the target location. After the measurementis taken, the handle 26 can be actuated to return the measuring cordsupport mechanism 16 to the retracted state, and the tool 10 withdrawnfrom the patient.

The tool 10 is described above as a dedicated measurement instrument. Inother embodiments (not shown), the measuring cord can be incorporatedonto other tools such as the CSD delivery tools described in theinternational applications referred to above in the background section.For example, the measuring cord can be incorporated onto theretractable/extendable CSD deployment mechanism shown in theinternational applications (i.e., the deployment mechanism would serve adual function), or a separate measuring cord support mechanism inaddition to the CSD deployment mechanism can be used.

The measuring cord 14 can be radiopaque to enhance its visibility underfluoroscopic or other imaging modalities during the use of tool 10(e.g., as an aide to positioning the measuring cord). In otherembodiments (not shown), the measuring cord 14 can have radiopaque orother markers at predetermined locations. These markers can be viewedunder an imaging modality (e.g., during an echocardiogram (ECHO) ortransesophageal echo (TEE)) to determine the size of the heart. Themarkers can be made distinguishable from one another to enhance theaccuracy of the measurement reading. In still other embodiments (notshown) the measuring cord can be color coded to facilitate measurementreadings. Yet other embodiments of the invention make use of otherstructures or approaches for determining the size of the heart based onthe length of the cord extended during the deployment of the measuringtool and for providing a visual display representative of the measuredheart size. For example, an instrument operatively coupled to theretraction mechanism can measure and provide a visual indication ofheart size based on the length of the measuring cord withdrawn from theretraction mechanism. Windows with indicia or other features enablingmeasurement readings can also be located on the support members 30.

FIGS. 4 and 5 illustrate a measuring tool 110 in accordance with anotherembodiment of the invention. As shown, a suction cup 121 is located onthe distal end 120 of measuring tool 110. The suction cup 121 isconnected to a vacuum source through a tube (not shown) that extendsthrough all or a portion of body 112. A valve (not shown) on body 112 orelsewhere can be used to control the application of the vacuum to thesuction cup 121. The suction cup 121 functions as a releasable suctiondevice to hold the measuring tool 110 on the patient's heart and tostabilize the heart during the measurement procedure (including duringthe deployment and withdrawal of the measuring cord support mechanism116). For example, when the measuring cord support mechanism 116 is inthe retracted state shown in FIG. 5, the suction cup 121 can bepositioned adjacent to the apex of the patient's heart and connected tothe vacuum source to secure the body 112 to the heart. Support mechanism116 can then be deployed to the extended state while the suction cup 121provides traction holding the body 120 to the heart. The vacuum sourcecan be disconnected from the suction cup 121 when the traction providedby the cup is no longer needed (e.g., after the support mechanism 116 isreturned to its retracted state). Other than the inclusion of thesuction cup 121 and any associated structures such as the vacuum tubeand valve, tool 110 can be substantially the same as or similar to tool10 described above, and similar features are identified by similarreference numbers.

FIG. 6 is an illustration of a heart size measuring tool 110′ inaccordance with another embodiment of the invention having ties 145′connecting adjacent support members 130′. FIG. 7 is a detailedillustration of one of the ties 145′. The ties 145′ open and collapsewith the support members 130′ when the support mechanism 116′ is movedbetween the extended and retracted states, and help keep the adjacentsupport members properly spaced (e.g., generally equidistant) from oneanother. The ties 145′ provide this function by providing resistance toany forces that might tend to cause the support members 130′ to collapsetoward one another. In the illustrated embodiment the ties 145′ arefolded elongated members such as malleable metal strips having theiropposite ends attached to the support members 130′ (e.g., by welds oradhesive 143′). Other structures for maintaining the spacing between thesupport members 130′ can be used in other embodiments (not shown). Forexample, physical stops on the measurement cord that engage the guideson the support members can be located at predetermined spaced-apartlocations on the measurement cord to provide or limit the maximumdistance between the support members. Other than the inclusion of theties 145′, tool 110′ can be substantially the same as or similar to tool110 described above, and similar features are identified by similarreference numbers.

In this and other embodiments, the support members can have stiffnessesthat vary along the length of the members. Alternatively or in addition,the stiffness of the support members can be different in differentdirections. For example, variable thickness can be provided by internalmovable stylets, inflation, changing thicknesses and changingcross-sectional shapes along the length of the members. By way ofexample, the dimension of the members in a radial direction with respectto a longitudinal axis through the tool 10 can be smaller than thedimension in the circumferential direction, enabling the support membersto be relatively rigid in connection with movement around the heart, yetrelatively flexible when moved toward or away from the heart. Thesupport members can also be malleable (e.g., metal or metal reinforcedpolymer) so they can be shaped by the physician or other personoperating the tool.

FIG. 8 is an illustration of heart size measuring tool 210 in accordancewith another embodiment of the invention. One or more radiopaque orother markers 251 (e.g., piezoelectric crystals) are located at spacedapart locations along the length of the support members 230. A pluralityof markers 251 are shown in each support member 230 in the illustratedembodiment, including a marker on the distal end of the support members.The markers 251 can be coded or otherwise made uniquely identifiable ordistinguishable from one another. Fluoroscopic, ECHO, TEE or otherappropriate imaging modalities can be used to image the measuring tool210 when the support members 230 are positioned on the patient's heart,and the locations and spacing of the markers 251 can be used todetermine the size of the heart. For example, a fluoroscopic image takengenerally parallel to the longitudinal axis of the tool 210 will showthe markers 251 in a generally circular pattern. The external diameterof the heart can be interpolated and estimated from this image. Otherthan the inclusion of the markers 251, tool 210 can be substantially thesame as or similar to tool 10 described above, and similar features areidentified by similar reference numbers. Still other embodiments of theinvention (not shown) have a support mechanism with markers such asthose of the embodiment shown in FIG. 8, but do not include themeasuring cord and associated components such as the retractionmechanism and scale.

Markers 251 can then enable fluoroscopic or other imaging-basedestimates of the longitudinal length of the heart and/or CSD. Dimensioninformation for both length and circumference are available,facilitating the selection of the most appropriately-sized CSD forimplantation. Similarly, this feature will enable “mapping” of theheart. The circumference of the heart at planes parallel to the base atlocations between the base and apex of the heart can be measured. Thisinformation can be used to estimate the surface area/shape of the heart.This additional information can further enhance correct CSD sizeselection.

FIG. 9 is an illustration of a heart size measuring tool 310 inaccordance with another embodiment of the invention. As shown, the tool310 includes one or more deflection sensors 361 located on each supportmember 330 (a plurality of sensors 361 are shown on each support memberin the illustrated embodiment). Sensors 361, which can for example bestrain gauge sensors, are operatively connected to an instrument unit365 (e.g., by wires, not shown, through cable 363). The instrument unit365 provides any drive power or signals needed for operation of thesensors 361. When the support mechanism 316 is positioned around thepatient's heart, the support members 330 will be deflected by amountsrepresentative of the size of the heart. Deflection signalsrepresentative of the deflection of the support members are received andprocessed by the instrument unit 365 to provide information (e.g., adisplay) representative of the heart size. Other than the inclusion ofsensors 361 and instrument unit 365, and the lack of a measuring cordand associated components such as the retraction mechanism and scale,measuring tool 310 can be substantially the same as or similar to tool110 described above, and similar features are identified by similarreference numbers. In still other embodiments (not shown) the sensors onthe support members include transmitting and receiving devices coupledto an instrument unit. In these embodiments the instrument unit can useDoppler or other methodologies to detect the relative positioning of thesensors and produce a heart size measurement.

FIG. 10 is an illustration of a heart size measuring tool 410 inaccordance with another embodiment of the invention. As shown, the tool410 includes a plurality of sensor electrodes 451 located on eachsupport member 430. Sensor electrodes 451 are connected to an instrumentunit 467 by wires (not shown) through cable 469. Sensor electrodes 451and instrument unit 467, which can, for example, be electrocardiogram(ECG) electrodes and instrumentation, are used to map the electricalpotentials across the surface of the heart while the tool 410 is alsoused to measure the heart size. The measuring tool 410 can be moved(e.g., rotated) to place the sensor electrodes 451 at differentlocations on the heart to enable electrical potential measurementsacross the surface of the heart. Other than the inclusion of sensorelectrodes 451 and instrument unit 467, tool 410 can be substantiallythe same as or similar to tool 10 described above, and similar featuresare identified by similar reference numbers. The sensor electrodes 451can also be used to locate the measuring tool 410. The electrocardiogramsignal produced by the heart has different characteristics above andbelow the A-V groove. By monitoring these signals using the sensorelectrodes 451, and in particular using the signals from electrodes nearthe ends of the support members 430, the location of the A-V groove canbe identified.

FIGS. 11-13 are illustrations of a heart size measuring tool 510 inaccordance with another embodiment of the invention. As shown, the tool510 includes a support mechanism 516 having two support members 530. Themeasuring cord 514 extends from the body 512 along each support member530 through guides 540, and between the guides 540 at the ends of thesupport members. Support members 530 are connected to actuatingmechanism 518. Actuating mechanism 518 can be actuated to move thesupport members 530 between a retracted position shown in FIG. 11 and anextended position shown in FIGS. 12 and 13.

Measuring tool 510 also includes a measurement actuator 555 coupled toone or both of the support members 530. The measurement actuator 555 isoperated to drive the support members 530 between the unactuatedmeasurement position shown in FIG. 12 to an actuated measurementposition. As shown in FIG. 12, the support members 530 can be positionedadjacent to one another in the unactuated measurement position. Thesupport members 530 are shown in a partially actuated position in FIG.13, with the support members spaced from one another to extend themeasuring cord 514. The support members 530 can have features of any ofthe embodiments described above.

The operation of measuring tool 510 can be described with reference toFIGS. 11-15. After the distal end 520 of the body 512 is positionedadjacent to the heart, the actuating mechanism 518 is operated to movethe support mechanism 516 from the retracted position shown in FIG. 11to the extended position shown in FIG. 12. The tool 510 is thenmanipulated to position the distal ends of the support members 530 atthe target measurement location on the heart. When the support mechanism516 is initially moved to the extended position the support members 530can be in an unactuated position with respect to one another. Themeasurement actuator 555 is then operated to move the support members530 with respect to one another to extend the measuring cord 514 alongthe measurement target on the heart. In one embodiment of the invention,one of the support members 530 remains stationary, and the other supportmember is revolved around the heart. FIG. 14 shows the support members530 in a partially actuated position with the measuring cord 514extended along a portion of the heart near the A-V groove. FIG. 15 showsthe support members 530 fully actuated, with the measuring cord 514 inthe measurement position extended around the heart at the A-V groove.The measured dimension of the heart can be read from scale 519 when themeasuring cord 514 is in the measurement position. Magnets or otherstructures on the support members 530 can releasably lock the supportmembers together after one of the support members has fully moved aroundthe heart with respect to the other support member and contacts theother support member, thereby aiding the measurement. After themeasurement is completed, the measurement actuator 555 can be operatedto return the support members 530 to the unactuated position. Theactuating mechanism 518 can then be operated to retract the supportmechanism before removing the tool from the patient. Other than thesupport mechanism 516 and measurement actuator 555, tool 510 can besubstantially the same as or similar to tool 10 described above, andsimilar features are identified by similar reference numbers.

Measuring tools in accordance with the invention offer a number ofimportant advantages. They are relatively efficient to operate and makeuse of surgical access incisions that will be used for the delivery ofthe CSD. The tools are capable of providing accurate measurements at anydesired location on the heart. Enhanced CSD sizing is enabled sincemeasurements of the heart size can be made relatively close in time tothe delivery of the CSD. The need for other imaging modalities used forheart size measurement can be eliminated. Other functionality such aselectrical mapping can be provided concurrently.

Although the present invention has been described with reference topreferred embodiments, those skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the invention. For example, more than one measurement cordcan be used. Other approaches for mounting the measuring cord to thebody, and for reading the measurements from the cord, can also be used.Features of the different embodiments of the invention described abovecan also be combined in different combinations. For example, the ties ofthe embodiment shown in FIG. 6 can be incorporated into otherembodiments of the invention.

The invention claimed is:
 1. A method for measuring a size of apatient's heart, the method comprising: inserting into a patient's bodythrough a surgical access incision a distal end portion of a heartmeasurement tool having a suction cup and a plurality of elongatesupport members that are longitudinally extendable and retractable inrelation to the suction cup; positioning the suction cup adjacent to anapex of the patient's heart while the suction cup is positioned distallyof the plurality of elongate support members; after positioning thesuction cup, extending the plurality of elongate support membersdistally past the suction cup such that distal portions of the pluralityof elongate support members extend around at least a portion of thepatient's heart, and after extending the plurality of elongate supportmembers, determining the size of the patient's heart using a scaledisposed on a proximal portion of the heart measurement tool.
 2. Themethod of claim 1, wherein said determining the size of the patient'sheart includes determining the size of the patient's heart as a functionof a length of measuring cord extending around the patient's heart. 3.The method of claim 1, further comprising imaging the heart measurementtool when the plurality of elongate support members are extendeddistally past the suction cup, and wherein said determining the size ofthe patient's heart includes determining the size of the patient's heartas a function of the imaging.
 4. The method of claim 1, wherein thedistal end portion of the heart measurement tool imagable heartlongitudinal length indicia, and wherein the method further includesimaging the heart measurement tool and determining heart length.
 5. Themethod of claim 1, wherein said determining the size of the patient'sheart includes mapping the size of the patient's heart by measuringlongitudinal length of the patient's heart and circumference of thepatient's heart at a plurality of locations between an apex and base ofthe patient's heart.
 6. The method of claim 5, wherein said measuringthe longitudinal length of the patient's heart includes imaging markerson the heart measurement tool.
 7. The method of claim 5, wherein saidmeasuring the circumference of the patient's heart includes extending aflexible measuring cord around the circumference of the patient's heart.8. The method of claim 1, wherein the heart measurement tool includes: atubular body, the suction cup disposed at a distal end of the tubularbody; a flexible measuring cord having length indicia, the plurality ofelongate support members supporting the flexible measuring cord; and anactuating mechanism slidably mounted to the tubular body and operable toextend and retract the plurality of elongate support members in relationto the suction cup.
 9. The method of claim 1, wherein the heartmeasurement tool includes: a tubular body, the suction cup disposed at adistal end of the tubular body; a plurality of imageable markers on theplurality of elongate support members; and an actuating mechanismslidably mounted to the tubular body and operable to extend and retractthe plurality of elongate support members in relation to the suctioncup.
 10. The method of claim 1, wherein the heart measurement toolincludes: a tubular body, the suction cup disposed at a distal end ofthe tubular body; a plurality of deflection sensors on the plurality ofelongate support members, the plurality of deflection sensors providingelectrical signals representative of elongate support member deflectionand the size of the patient's heart when the plurality of elongatesupport members are in the extended state; and an actuating mechanismslidably mounted to tie tubular body and operable to extend and retractthe plurality of elongate support members in relation to the suctioncup.